print ("成绩判断")

cnt = input("请输入分数：")
cnt1 = "该同学的成绩为"

while cnt.isdigit() == False:
    cnt = input("请输入数字：")

score = int(cnt)

if 90 <= score <= 100:
    print (cnt1 + "优秀")

elif 80 <= score < 90:
    print (cnt1 + "良好")

elif 60 <= score < 80:
    print (cnt1 + "合格")

elif 0 <= score < 60:
    print (cnt1 + "不合格")

elif score < 0 or score > 100:
    print ("成绩输入错误")
